1. Field of the Invention
This invention relates to a surgical instrument, such as an energy based surgical device.
2. Background Art
Energy-based surgical devices (EBSDs),which use a variety of energy sources (electrical, radio frequency, and ultrasonic), have been adopted widely for nearly all types of surgery due to their ability to effectively and rapidly control bleeding. EBSDs have been adopted widely for nearly all types of surgery including neurosurgery, orthopedics, gynecology, urology, general surgery, thoracic surgery, plastic surgery, and otolaryngology. Despite their advantages, the success of EBSDs has been tempered by the recognition that these devices can lead to collateral tissue damage due to thermal and/or electrical spread outward from the instrument.
For example, electrosurgery (monopolar and bipolar) involves the use of alternating current in the radio frequency (RF) range to generate heat for cutting and coagulating tissue. In bipolar electrosurgery, opposed grasping members are used to clamp tissue therebetween for coagulation, wherein the grasping members comprise electrodes of opposite polarity. As electrical energy passing through the tissue is transformed into heat, the tissue is desiccated and the loss of water produces an increased electrical resistance. As a result, surrounding tissue becomes relatively less resistive to electrical current and the current's pathway will switch course, resulting in a spread of thermal energy to tissue outside of the grasping members. This makes predicting the route current will take very difficult and not intuitive, and may lead to unintentionally damaging nearby tissue.
In addition, medical personnel may not always be able to visualize the thermal spreading because of obstructing tissue structures, especially during an endoscopic procedure. The limited field of view and narrow focus on a small area may allow thermal spread to occur unnoticed, potentially causing damage to vital structures. When performing electrosurgery or ultrasurgery in a laparoscopic environment, the presence of an insufflating gas having a low heat capacity may result in instruments not cooling as rapidly, which may further increase the potential for thermal damage.
Therefore, it is desirable to control the thermal spread from EBSDs in order to minimize unwanted thermal damage to surrounding tissues during surgical procedures as well as reduce patient recovery times and post-operative complications.